Certain titanium IV pyrophosphates have been described in the literature. See U.S. Pat. No. 4,122,062. These compounds, which both have hydrolyzable and non-hydrolyzable groups, are useful as coupling agents for organic materials, such as elastomers and plastics, and particulate fillers. Conventionally, the pyrophosphaates are prepared by the condensation reaction of a dialkyl pyrophosphoric acid with a tetraalkoxy titanate whereby one mole of alcohol is liberated for each mole of the di-substituted pyrophosphoric acid reacted. Other analogous processes, such as the reaction of titanium tetrachloride with alcohol and the di-substituted pyrophosphoric acid are also feasible. Such reactions liberate hydrogen chloride.
While the foregoing organo-titanate pyrophosphates thus prepared are useful as coupling agents in many applications, the process described suffers from certain drawbacks. Firstly, the by-products generated are often difficult to separate from the desired product; and, secondly, even trace amounts of these byproducts render the pyrophosphates unsuitable for certain applications. For example, traces of hydrogen halides are inimical to basic systems and epoxy formulations, and small quantities of alcohol are detrimental to isocyanate groups.